Death-by-9-Volt Possible?
5 Comments Published by Joel March 9th, 2007 in Gadgets, Survival. Share This
Though unconfirmed, the accompanying technical explanation of this ancient Darwin Awards winner gives it a measure of believability. The story goes that a curious sailor, having determined the electrical resistance of his skin, attempted to discover the resistance of his blood… by jamming the ends of a multimeter’s probe, powered by a 9-volt battery, into his thumbs. He was killed, they say, when 90mA of current skipped across his heart.
A purported Navy petty officer explains:
How, you might ask, with only a 9V battery? Easy. One of the “rules of thumb” that the Navy teaches is the 1-10-100 rule of current. This rule states that 1mA of current through the human body can be felt, 10mA of current is sufficient to make muscles contract to the point where you cannot let go of a power source, and 100mA is sufficient to stop the heart. Let’s look at Ohm’s law. Ohm’s law (for DC systems – I will not discuss AC here) is written as E=IR, where E is voltage in volts, I is current in Amps, and R is resistance in Ohms.When we did the experiment in the electrical safety class to determine our body’s resistance, we found a resistance of 500K Ohms. Using 9V and 500K Ohms in the equation, we come up with a current of 18 microAmps, below the “feel” threshold of 1mA. However, removing the insulation of skin from our curious sailor here, the resistance through the very good conducting electrolytes of the body is sharply lower. Around 100 ohms, in fact, resulting in a current of 90mA – sufficient to stop our sailor’s heart and kill him.
Ohms and amps make my brain’s balls hurt, so I’ll buy his explanation with no further analysis. But I have to ask: Why aren’t more people wiring up 9-volts to a pair of sharp wires and killing people by jamming the points into the skin? Seems like a pretty good weapon. Hell, you could lash it to the end of a spear. (I hope I haven’t just prompted a rash of 9-volt killings.)
Resistance is Futile [DarwinAwards.com]
I’m pretty sure even if this is true the current would not get anywhere close to the heart. The electric would take the shortest path to its ground. So like a stun gun it would hurt where it was touching but wouldn’t get anywhere else.
Sigh.
Rather than describe how this couldn’t happen, I sparked up two of my many, many multimeters and set one to measure resistance, the other voltage and then current.
Output voltage in resistance mode: 0.3VDC.
Output current in resistance mode: 0.3mADC
I can think of electrical test devices that can really, really hurt you, but the multimeter seems unlikely, and the other device in question will zot you good even through your skin.
Please take it easy on spreading the folklore – it hardly needs the help.
I can say from experience that this is pretty unlikely, as I’ve done it, more or less. In middle school we were doing an, um, unsupervised experiment with making hydrogen. Our power source was about 26 9-volts wired in series (for a total of 234 volts, in theory).
The problem was wet hands+loose wires. While pulling the bare leads out of the test tube, I accidentally grabbed both ends. The instant tensing of the muscles going from one hand across to the other was and interesting experience.
I’ve tested many 9 volt batteries by placing the output terminals to my tongue. A fresh battery gives quite a zap but I’m still able to walk, talk and think cohesivelyyyyyyyyyyy.
erhhhhhh nebr mindddddddddd
Its all about the path of current here. If you connected one pole of the 9V into the flesh (penetrating the skin) on one hand and did the same with the other pole of the 9V on the other hand, the source current capability of a new 9V (max about 150mOhms) given the bodies fatty tissue and vascular (blood) resistance across finger to finger is enough to shock the heart muscle. Again, since the path is across the heart, not across your tongue. DON’T TRY THIS – IT WORKS!